Inhibited detergent composition



Patented Apr. 18, 1939 l 1 i l DETERGENT ooMrosmoN Carroll L. Griflith and Lloyd A. Hall,

Chicago,

IlL, assignors to The Griiiith Laboratories, Inc.,

' Chicago. 111., a corporation of Illinois No Drawing. Application July 20, 1938', Serial No. 220,348

; 12 Claims.

The present invention relates to alkaline detergent baths and compositions to produce the same, useful particularly for cleaning metal surfaces of. tin, zinc, iron or aluminum, without deleterious action such as corrosion, dissolution,

- spangling, or checking.

In our prior application Serial No. 66 ,436, flled' February 29, 1936, we have described and claimed compositions of matter involving water-soluble ingredients which may be taken up in water to produce the desired cleaning bath. The present application is generic to said prior application, and is a continuation in part thereof. It aims to disclose mixtures in which the ingredients 'are in not all of the water-soluble type, which may be acted upon by water to produce a solution of the same general nature for use as the cleaning bath. Fundamentally, the utility of the invention is in the bath, wherein water predominates. 'Commercially, however, the bath is not a satisfactory article of commerce, so the ingredients minus the water are compounded for ,sale. The most practical composition involves water-soluble constituents as taught in said prior application. The 25 present application shows that the ultimate result may be accomplished by use of diiferent compositions- The use of alkaline agents is well known for cleaning metal ware of zinc, aluminum or tin 30 plate, such as milk cans, bakin Dans, etc., whichhave .011, grease or fat, burned-on flour, milk curds, etc. It is realized that baths of these agents are usually injurious to the metal in the concentrations and at the elevatedtemperatures 35 and the time of action ordinarily employed. It is also known that inhibit 'gagents are added to minimize or prevent Some a: these inhibited detergent compounds are veiieetive whn the metal pieces are washed in o wooden, glass or enamel tanksor under other conditions which do not produce additional deleterious influences. For example, theremay be found baths which are effective in a glass tank, but which 'are not eflective in agalvanized iron 5 tank, or in an iron tank, when the metal being cleaned is in contact with the metal of the tank. The tank metal and the metal piece to be cleaned establish electrical contact and are in a common bath, thus establishing galvanic action. By 50 this condition different electrical potentials between the two meta and the solution cause a galvanic flow of elec ricity, or alteration of the single potential which exists between each metal alone and the cleaning bath. The same condi- 5s tions may occur in a non-conductive tank where such deleterious action.

'difierent kinds of metal. pieces are being cleaned in contact with each other. The alteration of conditions as a result-of these galvanic couples can be sumcient to produce corrosion or injury with cleaning baths which are otherwise satisfac- 5 tory.

The present invention aims to produce a detergent compound whichis more iniiver'sally effective for various metals to be cleaned, and for use in glass, zinc, galvanized iron,,or iron tanks, 10 and for use simultaneously with diilerent metals to be cleaned. It is an object to provide a compound in solid form to befadded to water to form a bath, or else to provide the. bath itself. Although the invention provides a bath which is 'efiective where galvanic force exists, it should be understood that the conditions which are encountered in the galvanic action are the result of forces which exist in the absence of a galvanic couple, namely the electrical potential existing between the bath and the metal to be, cleaned. This potential is involved in the deleterious ac- 1 tion to .be avoided. The bath, therefore, as a whole, creates a favorable single potential between the bath and the metal, which potential is such that it remains favorable when galvanic conditions are also encountered.

The detergent compounds in this artare generally used in concentrations varying from /2 to 8 ounces per gallon, and in the work leading. to this invention this range of concentration has been more particularly studied. The general statemerits herein made are with reference to such a range of concentration, but it is not to be assumed thatthe general statements are not applicable above and below this range. The temperature and time of exposure to the cleaning agent also have a bearingcn the action, and unless otherwise specified general statements are to be considered' with reference to conditions commonly 40 encountered in commercial practice.

Common alkaline reacting detergents are soda ash, water soluble inorganic alkaline detergents.

'caustic soda,.tri-sodium phosphate, sodium silicate, borax, etc. Several of these may be used in weak solutions, such as 0.15% to '.3% concentration when cold without giving corrosion, or other deleterious action, but the cleaning action is not efiective. when heated to secure eilective cleaning,.there is also corrosion or other adverse action. Addition agents for inhibiting corrosion are recognized but 'they-havelimited or specific action dependingupon concentration and kindv of alkali, concentration. of inhibitlngsa'gent, temperature, and time. hypochlorite is one such agent. Chromates are recognized inhibitors for mild alkaline detergents. Perborates have been used. Hypochlorites are also known. By some it is considered that the function of such inhibitors is the same because these are oxidizing agents. However, we have established that this is not true.

Calcium hypochlorite is not a successful inhibitor for use with the general run of alkaline detergents when used for tin or aluminum surfaces, and for use in glass, iron, zinc or galvanized tanks. Neither are zinc salts, such as zinc sulphate, suitable inhibitors under these conditions. The present invention is based upon the discovery that calcium hypochlorite and zinc salt such as zinc sulphate, may be used in combination as a corrosion inhibiting mixture for alkaline detergents under the described conditions.

The invention appears to involve the essential combination of hypochlorite ions and zinc ions in the solution, where detergent alkali is present. We have found that perborate is not an equivalent of hypochlorite in the invention. For example to a composition:

. Parts by weight Trisodium. phosphate monohydrate 42.5 Soda ash 42.5 Anhydrous zinc sulphate 10 we have added:

Case A-sodium perborate 5 and v v Case 'B-high test calcium hypochlorlte 5 Case A.-The composition at a concentration of 2 ounces per gallonshows no ,corrosion on tin and aluminum in 48h0urs at 70-75 F., but at the boiling temperature it shows heavy corrosion on tin in 1 hour and minutes, and on aluminum in minutes.

Case B.At the same concentration as'Case A, the bath at '70-75 F. shows no corrosion on tin and aluminumin- 48 hours, while at boiling temperatures no corrosion of tin occurs, yet there is corrosion of aluminum.v However, the protection of aluminum depends upon the use of another ingredient, namely, sodium silicate, yet in this instance, the perborate is not an equivalent of hypochlorite as shown by the following:

" To a composition: v I

7 Parts by weight. Trisodium phosphate monohydrate Soda ash 39.75 Sodium metasilicate (Metso) 20 Anhydrous zinc sulphate 10 we have added: v Case C--sodium perborate"; 5 and Case D-high test calcium hypochlorite 5 because perborate on heating loses oxygen which readily escapes, while hypochlorltes on heating lose chlorine, which is highly soluble. The hypochlorites provide complex oxygen-chlorine radicals which are somewhat unstable in solutions limited to alkali metal and alkali earth cations, but which seem to be far more stable when zinc ions are present. Zinc has the faculty of forming stable compounds with both oxygen and chlorine.

Therefore, we believe that the presence in the bath of zinc cations and of hypochlorite ions results in a combination making the bath a successful corrosion inhibiting'alkaline bath.

In addition to the examples Case B and Case D of the invention wherein water-soluble constituents are used (our prior application), the following examples are given to show the use of waterinsoluble zinccompounds which become soluble in a bath in he presence of the companion ingradients of the examples, sufflciently to provide the desired inhibiting action.

In Example E the same weight of zinc carbonate is used in place of zinc hydroxide.

- I Exsurm G (Example 2 of the prior application) Parts by weight Trisodium phosphate monohydrate Anhydrous sodium carbonate; 39.75 .High test calcium hypochlorite i 6 Anhydrous zinc sulphate 9 Sodium metasilicate 15 Wool orange 2-G .25

' EXAMPLE H Zinc hydroxideis substituted for zinc sulphate in Example G.

Exeur m I Zinc carbonate is substituted for zinc sulphate in Example G.

EXAMPLE "J (Example 4 of prior application) Partsbyweight Borax 24.75 Sodium metasilicate 15 -Anhydrous sodium carbonate High test calcium hypochlorite 5 Anhydrous zinc sulphate 10 Wool orange 2-G -l .25

, W EXAMPLE K Zinc oxide replaces zinc sulphate in Example J.

' EXAMPLE L Zinc hydroxidereplaces zinc sulphate in Example J.

Exsmrnn M Zinc carbonate replaces zinc sulphate in Example J.

Examrrs N i (Example 5 of prior application) Wool orange 2-G EXAMPLE E Parts by weight Trisodium phosphate monohydrate 32.50 Soda ash 32.25

Sodium metasilicate-.. 20 High test calcium hypochlorite 5 Zinc hydroxide 10 Wool orange 2-G .25

Exmrm F Exlmrml O, Zinc hydroxide replaces zinc sulphate in Example N.

ample Q.

EXAMPLE S 55 Zinc hydroxide replaces the zinc sulphate of Example Q. This compmition is like Example E.

Exnlrnr: T

' Zinc carbonate replaces the zinc sulphate of to Example Q. This composition is like Example F.

Exam: U Zinc hydroxide replaces the zinc sulphate of Case 8 above. a EXAlilPLE v Zinc carbonate replaces the zinc sulphateof Case 3 above.

Examu: W

,0 In any of the foregoing 5 parts of calcium hypochlorite (70-72% available chlorine) is replaced by 6 parts Of sodium hypochlorite NaC1O.2 /H2O.

Thus in Example G, 7.2 parts of the sodium hypochlorite is used.

,5 It will be observed from the above formulas thatthe. composition is solid, being amixture of the separate ingredients named. These are to be used in concentrations of to-8 ounces per gallon of water. The resulting bath is not neces-' o sarily a solution of these ingredients unchanged.

It must be recognized that there may be reactions between ingredients when water is present,

. that new compounds are formed; that even precipitates maybe formed; that the solution ar- 5 rives at some equilibrium composition at definite conditions and is'variable with change of conditions; and that in use this bathmay change con siderably in its composition. Precipitates may not form in making a solution, but may tend to form, and they may form inuse of the bath for cleaning. v

R The inhibitingiaction'may be due to formation of'an inhibiting film on the metal, or to the tendency to form an inhibiting film. Frequently in chemical action there is a force tending to pro-- duce a certain result. Theaction does not occur until a certain threshold value of the force is attained, yet the mere existence of the force without a visible result therefrom, is a vital factor a in a process.

Such a condition has been observed in studying the present invention, but there is'reason to believe that it is. notlthe only instance of such con ditions. This observation relates to the presence {or zinc in the bath.

. I Zinc oxide replaces the zinc sulphate of Ex- There have been observed certain conditions under which zinc from the solution plates out.

. electrochemically or galvanically, onto the metal being cleaned. This indicates that a certain threshold value for a zinc-depositing force has been exceeded, resulting in thezinc deposition. On the low side of this limiting value for the force, the tendencyfor'zinc to plate out must exist, yet the zinc'does not deposit visibly. 'It may. be depositing invisibly at a rate equal to or less than a rate at which it is dissolved, so that the net result is no deposition.

It is'well recognized that where there is a tendency to plate onto a metal, there is little or no tendency for the metal to be dissolved'by the plating solution. From these facts and observations it isbelieved that the presence of zinc in thesolution is an important factor contributing to the inhibiting-action of the composition. It is quite likely that the zinc in solution acts to alter the potential difference beween the bath and the 'metal tube cleaned, 'from what the potential would be if the zinc were absent. However, the action of the soluble zinc appears to be joint with other ingredients.

Alkaline detergent part The invention may be practiced with the common alkaline detergents, but it is preferred that the less caustic ones be used, inorder to protect workers from caustic burns. Mixed alkaline demixture in the present invention has the advantage of protecting iron, zinc, tin and aluminum surfaces. Borax may be substituted for the trisodium phosphate monohydrate for the protection of these metals; Where sodium metasilicate is omitted from the mixture of alkalis, the composition does not protect aluminum, but it does protect the zinc, iron and tin surfaces. Those compositions not having the silicate are not efiective on aluminum under the regular condition of commercial usage. The alkaline detergent part of the whole composition may vary in a wide manner. In the final composition the alkaline detergent part is preferably 85% where the inhibiting part is: about 15%. The exact ratio is not critical andthe variations may be readily determined by simple experimentation. Sodium silicate is primarily of the alkaline detergent part, but as to aluminum it also falls in the inhibiting part. There are several forms of sodium silicate, and their specific effects may vary the efficiency or limiting proportions for a given set of. conditions. The sodium metasilicate is preferred to others, such as sodium orthosilicate because in the dry solid composition it creates better stability.

Inhibiting part In the bath, the essential inhibitors are the' a zinc in solution and in equilibrium with any zinc in suspension, and the hypochlorite salt. In

lit

making the bath directly, various compounds may be used. The two inhibiting ingredients may vary in their ratio to each other, and there will of course be one ratio which is more efiective for a certain alkaline agent or combination of them. This eificient ratio may also vary for the conditions of use, and with variations in the ratio between the alkaline part and the'inhibiting part. It is therefore not possible to set forth explicitly a definite emcient ratio.

The commercially preferred ratio and form is 1 part of calcium hypochlorite (high test commercially defined as having '70 to 12% available chlorine and containing about 3% of calcium chloride and 23% sodium chloride) and 2 parts of anhydrous zinc sulphate (about 36% zinc content) or its equivalent. For 85% content of the preferred alkaline mixture above described, and content of inhibiting part, the latter has the prefered ratio of lpar't' of commercial high test calcium hypochlorite and Z'parts of anhydrous zinc sulphate. If. this last ratio, is reversed the desired effect is not obtained. The critical limit is not subject to determination unless exact speclfications for use are given, and then there must be considered the extent to which the bath is allowed to deteriorate 'in use, before it is considgredients for any set ofconditions.

ered non-effective. I

The important ingredient in the commercial high test calcium hypochlorite is the combination or compound of calcium, oxygen and chlorine. The sodium chloride present in the form described is not any essential part of the invention, but its presence obviously plays a part in determining critical proportions of the essential in- There are on the market various forms of high test cal-=. cium hypochlorite, and in addition to the form having sodium chloride, there is a form having calcium chloride instead of sodium chloride. This may be used in the composition with appropriate adjustments, but it is not preferred where asolid-powder is marketed on account of the hygroscopic nature of calcium chloride. There are also available solid sodium hypochlorites which may be used, as well as sodium hypochlorite solutions that may be employed.

The examples The examples show wool orange 2-6, but this is merely an example of a dyestufi optionally added to give character or distinction to the composition and to the bath.

All the examples give adequate protection to iron, zinc, and tinned ware. Formulas having sodium silicate are adequate for iron, zinc, aluminum and tinned ware. These formulas give such protection when the temperature is maintained above 80 C. or higher and at the boiling point forextensive periods of time longer than commercially used to effect cleaning, such as 8 hours and even to 48 hours. The effectiveness of the inhibitor may be appreciated by the fact that any of the alkaline agents alone in the same concentration (such as 85% of the /2 to 8 ounces per gallon) at 70 C., give corrosive action on both aluminum and tinned ware in a few minutes, and immediately at, 100 C. If hypochlorite is left out, all will corrode the metals. I

The formulaof Case B is exceptional in that it will deposit zinc upontinned ware when the concentration istoo high, for example over about 5 onces per gallon. This is striking evidence of a function for zinc in the bath, at lower. concentrations where it is not deposited. The tendency arsaoas to deposit is no doubt an important part of the inhibiting forces.

Examples Q to T are given to represent a special condition of use wherein the resulting bath has been used at temperatures above 80 C. but without -boiling. There is initially, or is developed in use, a suspended precipitate which in boiling is agitated to come into contact with metal being cleaned. Where no boiling takes place this settles, and to avoid contact with the metal the parts being cleaned were suspended above the settled precipitate. In three hours heating there is no corrosion but a slight white precipitate forms on the metal which is easily removed. These and the other examples give no corrosion under boiling conditions.

The composition is preferred in a form which may be economically marketed. Hence ingredients are chosen which may be mixed to remain stable and non-reactive. The available-chlorine from the hypochlorite maybe fugitive and its retention is important. Absence of water is desirable to keep the mass stable. Steel drums are suitable containers for inducing stability in the compositions given; Although. there may be water of crystallization in some of the components (particularly the b orax,and the trisodium phosphate monohydrate) it is so closely bound that it is not detrimental to stability.

When the composition is dissolved reactions occur which vary with the composition and conditions. The bath may even become milky with some precipitate or insoluble suspension. Translent films may be formed on the metal to be cleaned, yet the cleaning action without .deleterious action on the metal is effected. The baths may be boiled, for example for 8 hours, with little loss of available chlorine. The bath itself is stable at the commercially useful dilution.

, It is to be understood that the bath itself is the functioning composition of the invention,

and that it may be described as the reaction product of the constituents named in the .formulas. One could make up the bath directly, and then there is more latitude in choice of ingredients. For example, sodium hypochlorite may be used in place of calcium hypochlorite. The substitution cannot readily be made commercially in the solid powder form because sulficiently strong sodium hypochlorite is not commercially available in solid form. The calcium form of hypochlorite is merely a means to employ hypochlorite in a strong solid form which with other ingredients produces a stable composition. The alkali emulsifles or saponifies the grease and fat and readily cleans other dirt or food residues.

The invention has several aspects as set forth herein. The formulas may be changed considerably from the examples given as indicated by the scope of the appended claims.- I

We claim:

l. A corrosicn inhibiting alkaline composition for cleaning zinc, iron and tin ware in an aqueoussolution thereof at from cold to boiling temperatures consisting by weight essentially of about 85% of water-soluble inorganic alkaline detergent, about 5% to 7.2% of a solid hypochlorite salt of a metal from the group consisting of alkali metals and alkali earth metals, and about 9% to 10% of zinc compound from the group consisting of water-soluble zinc salts, zinc oxide, zinc hydroxide and zinc carbonate.

2. A composition according to claim 1 in which the zinc compound is water-insoluble.

3. Acomposition according to claim 1 in which the hypochlorite salt is calcium hypochlorite.

4. A composition according to claim 1 inwhich the alkaline detergent material is a mixture of anhydrous sodium carbonate and trisodium phosphate monohydrate.

5. A composition according to claim 1 in which the part of the alkaline detergent to the extent of to by weight of the composition is a sodium silicate, whereby the composition forms a bath which also protects aluminum.

A corrosion-inhibiting composition for cleaning zinc, iron, tin and aluminum ware in an aqueous solution thereof at from cold to boiling temperatures consisting by weight essentially of from about to of water soluble inorganic alkaline detergent, from about 15% to 20% of sodium silicate, about 5% to 6% of calcium hypochlorlte, and about 9% to 10% of a zinc compound so from the group consisting of water-soluble zinc salts, zinc oxide, zinc hydroxide and zinc carbonate.

7. A corrosion-inhibiting mixture for addition to a water-soluble inorganic alkaline detergent 25 to render a bath of such material non-corrosive on zinc, iron, and tin ware at from cold to boiling temperatures, which consists by weight of about 1 part of a hypochlorite salt oi a metal from the group consisting of alkali metals and alkali earth metals, and about 2 parts 01' a zinc compound from the group consisting oi water-soluble zinc salts, zinc oxide, zinc hydroxide and zinc carbonate.

8. The method of inhibiting the action of aqueous solutions of inorganic alkaline detergents upon zinc, iron and tin ware at temperatures from C. to boiling which comprises adding to the detergent solution having by weight about parts of alkaline detergent, an inhibiting mixture consisting of about 5 to 7.2 parts of a solid hypochlorite salt of a metal from the group consisting of alkali metals and alkali earth metals and about 9 to 10 parts of a zinc compound from the. group consisting of water-soluble zinc salts, zinc oxide, zinc hydroxide and zinc carbonate;

9. The method 01' inhibiting the action 01' aqueous solutions oi inorganic alkaline detergents upon zinc, iron, tin and aluminum ware at temperatures from 80 C. to boiling which comprises adding to the detergent solution having. about 60 to 70 parts by weight of inorganic alkaline detergent, an inhibiting mixture consisting of about 15 to 20 parts by weight of sodium silicate, about 5 to 7.2 parts by weight 01' a solid hypochlorite salt of a metal from the group consisting of alkali metals and alkaline earth metals, and I about 9 to 10 parts by weight oi a zinc compound from the group consisting oi water-soluble zinc. salts, zinc oxide, zinc hydroxide and zinc'carbonate.

10. A corrosion inhibiting mixture for addition to a water-soluble inorganic alkaline detergent to render a bath oi such-material non-corrosive of zinc, ironand tin ware at from cold to boiling temperatures, which consists of about 2 to 3 parts by weight oi a. solid hypochlorite salt 01 a metal from the group consisting of alkali metals and alkali earth metals, and about 9 to 10 parts by weight or awater-insoluble zinc compound which is soluble to provide zinc ions in said bath.

11. A corrosion-inhibiting cleaning bath for zinc, iron and tin ware at from cold to boiling temperatures comprising an aqueous solution having from V: to 8 ounces per gallon 01' the products resulting on dissolution in water, of a mass initially represented by 'a composition comprising by weight essentially 85% of water-soluble inorganic alkaline detergent, available chlorine in hypochlorite form corresponding to 5% to 6% of high test calcium hypochlorite o! 70% to 71% available chlorine, and 9% to 10% of zinc compound selected irom the group consisting of water-soluble zinc salts, zinc oxide,

zinc hydroxide and zinc carbonate.

12. A' bath according to claim 11 which is also non-corrosive on aluminum in which the percentage by weight of alkaline detergent material includes from 15% to 20% byweight of sodium silicate; U v

csnaomnomm. m nimalism 

